Arylsulfonyl isocyanates are known to be useful intermediates in the production of a variety of compounds. They can be used for preparing hypoglycemic drugs as described in Logemann et al., Chem. Abs. 53, 18052g (1959) and Wojciechowski, J. Acta. Polon. Pharm., 19, 121-125 (1962), as well as for preparing novel herbicides such as those described in U.S. Pat. Nos. 4,127,405 and 4,120,691.
It is known in the art to prepare arylsulfonyl isocyanates by the reaction of the corresponding arylsulfonamides with phosgene in an inert solvent. As described in British Pat. No. 692,360, this reaction requires a temperature in the range of 160.degree. to 250.degree. C. as well as a large excess of phosgene.
U.S. Pat. Nos. 3,371,114 and 3,484,466 teach the preparation of arylsulfonyl isocyanates by phosgenation of arylsulfonamides in the presence of a catalytic quantity of a hydrocarbyl isocyanate. This reaction is carried out in an inert solvent at a temperature between 60.degree. and 200.degree. C.
The phosgenation of N-arylsulfonyl-N'-alkylureas at temperatures of from 0.degree. to 175.degree. C. to prepare arylsulfonyl isocyanates is described in U.S. Pat. No. 3,379,758.
In U.S. Pat. No. 3,689,549, the phosgenation of a sulfonamide in a sulfolane solvent is taught to produce a sulfonyl isocyanate of increased purity.
German Pat. No. 2,152,971 teaches a process for preparing sulfonyl isocyanates by reacting sulfonamides with phosgene in an inert solvent, in which the reaction is carried out in the presence of mono- and/or poly- primary amines in such an amount that there is less than 0.1 equivalent of primary amino groups per equivalent of sulfonamide groups.
U.S. Pat. No. 2,362,648 discloses a method for preparing isocyanates by reacting an amine with phosgene in the presence of a tertiary amine catalyst.
Although the prior art describes several processes for preparing arylsulfonyl isocyanates, there exists a need for an even more efficient and economical process for preparing these useful compounds.